So why is the C6 harder to kill behind a diesel?

The C6 didn't have lockup, right? That would make it hot as heck all the time.

Isn't the back end of the E4OD very similar to the C6, with a overdrive planetary and clutch set at the front? So why the disparity on the reliability.

And why the far more expensive repairs on the E4OD vs. the C6?